Grid-connected/Grid-islanded Smooth Switching Control of VSG Converter Based on Pre-synchronization

As global environmental pollution and global warming issues become increasingly severe, researches on grid-connected operation and control strategies of renewable energy generation such as photovoltaic and wind power have attracted more and more attention. The virtual synchronous generator (VSG) converter, as an interface for renewable energy grid connection, significantly enhances the integration capability of renewable energy. Therefore, studying the control strategies of VSG converters is of great significance. However, converters using conventional VSG control can cause significant current surges in the grid during mode switching, disrupting the stable operation of the grid. Based on this, researching seamless switching control strategies for VSG converters during grid connection and disconnection is urgent and important. This paper focuses on VSG converters and conducts research on issues of seamless switching control for VSG converters during grid disconnection. To address the problem of excessive current surges during grid disconnection with conventional VSG converters, a seamless switching control strategy for VSG converters during grid disconnection is proposed. For the grid disconnection/connection switching process, smooth switching can be achieved without the need for additional control methods. For the connection/disconnection switching process, a grid-connected/grid-islanded smooth switching control of VSG converter based on pre-synchronization is proposed, which is simpler and enables seamless switching compared to traditional pre-synchronization control methods.